Primulaceae. 217 



cylinder varies from 2 in the primary, and thin adventitious 

 roots of Pr.sibirica to 6 (Pr. nivalis); 4 seems the usual number 

 in the group Farinosae. The primary structure is retained 

 throughout the existence of the root, though, in very strong 

 roots of Pr. stricta I have found a few hadromal elements 

 apparently of secondary origin. The primary cortex of the 

 young roots is filled with starch, which is consumed during 

 the spring growth. The adventitious roots of Pr. egaliksensis, 

 Pr. sibirica, Pr. stricta and Pr. farinosa v. groenl. developed 

 during the preceding summer, were found to die away; the 

 primary cortical cells collapse and become empty, and in 

 the case of Pr. sibirica, the thickenings of the cell walls dis- 

 appear. In these roots of the preceding year, I have noticed 

 diminutive crystals of a calcium salt, especially in the outer 

 layer of the cortex; these were most frequent in Pr. stricta. 



The anatomical structure of the root of Dodecatheon 

 frigidum resembles most that of the Primulas. It differs 

 in its characteristic exodermis and in the longevity of the 

 epidermis. The number of hadromal rays in the adventitious 

 roots varies from 3 to 5, but the finer lateral roots have 

 only 2 rays. ■ The cells of the primary cortex have somewhat 

 thickened walls 



2. In contrast to the type described above, the roots 

 of Androsaces species pass quickly into the secondary stage. 

 An active cambium ring is developed, and forms numerous 

 vessels and wood-parenchyma toward the inside, and out- 

 wards leptome elements with somewhat collenchymatous 

 thickened walls. The epidermis and primary cortex lying 

 outside the endodermis, are thrown off. Through division 

 along the radial walls, the cells of the endodermis are 

 enabled to keep pace with the increase in thickness of the 

 central cylinder. 



II. All the species of the genus Primula described here 

 are characterised by an anomalous structure of the rhiz- 



